OH. XXXIII.] BILE. 50 1 



the metabolism of carbohydrates (glycogenic function) ; and in 

 connection with the metabolism of nitrogenous material 

 (formation of urea and uric acid). This second function we 

 shall discuss with the urine. The third function is the forma- 

 tion of bile, which must very largely be regarded as a subsidiary 

 one, bile containing the waste products of the liver, the results 

 of its other activities. This, however, it will be convenient to 

 take first. 



Bile. 



Bile is the secretion of the liver which is poured into the 

 duodenum ; it has been collected in living animals by means of a 

 biliary fistula ; the same operation has occasionally been performed 

 in human beings. After death the gall-bladder yields a good 

 supply of bile which is more concentrated than that obtained 

 from a fistula. 



Bile is being continuously poured into the intestine, but there 

 is an increased discharge immediately on the arrival of food in 

 the duodenum ; there is a second increase in secretion a few 

 hours later. 



Though the chief blood supply of the liver is by a vein (the 

 portal vein), the amount of blood in the liver varies with its needs, 

 being increased during the periods of digestion. This is due to 

 the fact that in the area from which the portal vein collects blood 

 stomach, intestine, spleen, and pancreas the arterioles are all 

 dilated, and the capillaries are thus gorged with blood. Further, 

 the active peristalsis of the intestine and the pumping action of 

 the spleen are additional factors in driving more blood onwards to 

 the liver. 



The bile being secreted from the portal blood is secreted at 

 much lower pressure than one finds in glands such as the salivary 

 glands, the blood supply of which is arterial. Heidenhain found 

 that the pressure in the bile duct of the dog averaged 15 mm. of 

 mercury, which is nearly double that in the portal vein. This 

 fact is of considerable importance, as it illustrates the general 

 truth that secretion is not mere process of passive filtration, but 

 that the cells exercise secretory force. 



The second increase in the flow of bile that which occurs 

 some hours after the arrival of the semi-digested food (chyme) in 

 the intestine appears to be due to the effect of the digestive 

 products carried by the blood to the liver, stimulating the hepatic 

 cells to activity : this is supported by the fact that proteid food 

 increases the quantity of bile secreted, whereas fatty food which 



